The present invention relates to a composition of matter having utility as a reagent for decomposing hazardous halogen-containing organic compounds, such as polychlorinated biphenyls (PCBs).
The potential hazard to health and the environment posed by the indiscriminate disposal of a variety of synthetic halogen-containing organic chemicals is well known. Compounds such as polychlorinated biphenyls, dichlorodiphenyltrichloroethane (DDT), decachlorooctahydro-1,3,4-metheno-2H-cyclobuta [c,d]-pentalen-2-one (Kepone.RTM.), and 2,4,5-trichlorophenoxyacetic acid, (2,4,5-T), although having demonstrated utility, have been found in recent years to be persistent environmental poisons, and, therefore, require a safe and effective means of disposal.
Halogenated organic compounds pose a difficult disposal problem because of the highly stable nature of the carbon-halogen bonds present therein. The bond energy of a carbon-chlorine bond, for example, is on the order of eighty-four kcal./mole. These compounds are not only resistant to biodegradation, they cannot be degraded in a practical and effective manner by any of the conventional chemical decomposition methods. In most cases, methods, such as chlorolysis, catalyic dehydrohalogenation, molten salt reactions, ozone reactions, and alkali metal reduction, do not achieve complete dehalogenation. Moreover, these prior art methods typically require expensive reagents, inert atmospheres, extensive temperature control, complex apparatus, substantial energy consumption, and the like.
PCBs present a particularly serious disposal problem. Once widely used as dielectric fluids in electrical equipment, such as transformers and capacitors, because of their excellent insulating properties, the use of PCBs was banned recently by the United States Environmental Protection Agency (E.P.A.) due to cumulative storage in human fatty tissue and reports of extremely high toxicity. In connection with the ban, the E.P.A. has promulgated rules under which the only available means for complete decomposition of extant PCBs and PCB-contaminated substances is incineration. However, incineration of PCB-contaminated materials in accordance with E.P.A.-approved procedures is decidedly wasteful since potentially recyclable materials, such as dielectric and hydraulic fluids, which may contain a relatively small amount of PCBs are destroyed in the process. To avoid such waste, it has been proposed to treat recyclable materials contaminated by PCBs with an absorbent, e.g., by passing the material through a bed of activated charcoal or a resin to selectively remove the PCBs from said material. Although PCBs are physically removed from the recyclable material in this manner, the disposal of absorbed PCBs still remains a problem.
Several chemical methods for decomposition of PCBs have been proposed employing high surface sodium, sodium/naphthalene, and sodium naphthalide. These methods have some notable limitations, however, in that the reagents are difficult to prepare, expensive to ship and unstable in storage. Moreover, the sodium-containing decomposition reagents proposed heretofore are sensitive to oxygen and to water and therefore cannot be used reliably under field conditions.
Aside from the PCB disposal problem, there are significant quantities of other waste or excess halogen-containing organic chemicals presently being stored by manufacturers, processors or consumers, which chemicals must be disposed of eventually in an environmentally acceptable manner. It is estimated that the amount of hazardous chemical substances generated by industry increases by about three percent annually. Viewed realistically, storage of toxic chemicals can only be considered a stop-gap measure while efforts to develop a safe, practical and effective process for their disposal continue.